The normal menstrual cycle of all women is always modulated by a variety of ovarian steroids and peptides, among which estrogen is the primary regulator. Example: early in the cycle the concentration of the estrogen in the blood is very low, in the order of 20-60 pg/mL, while during the 6 days fertile period (in the middle of the 28 days cycle) it leaps to 200 pg/mL, or up to 10 times. (See FIG. 1(a)) Contrary to that, the variations of the body temperature (which is also modulating the menstrual cycle, see FIG. 1(b), and used by many women to determine the ovulation) changes only in the interval of 37(xe2x88x920.3+0.5)xc2x0 C., making the temperature inacurate fertility indicator. Additionally to the above, the estrogen is known to coordinate the systemic response during the ovulatory cycle, including the growth and maintenance of the reproductive tract, pituitary, breasts, and other tissues. Studying the estrogen behavior as above narated, these inventors realized that is possible to engineer a good NON INTRUSIVE FERTILITY-NON FERTILITY DEVICE-INDICATOR FOR WOMEN, using the variations of the estrogen as indicator. Studying further the problem the inventors realized that the best way to perform that task is to employ the linear and the circular polarized light, as well as a quick spectral analysis to detect the estrogen (not in the blood, but) in the saliva. That way these inventors engineered a high accuracy non intrusive fertility choice device, as special object of this invention. Other objects of the invention should become apparent to those skilled in the art,upon reading the disclosure.